The invention is based on a packaging container having a pressure relief valve as set forth herein. In a packaging container of this type, known for instance from U.S. Pat. No. 2,927,722, the walls are shaped from a flexible packaging material, and the membrane that forms the valve member is secured on the walls over an opening that has a relatively large cross section. This arrangement has the disadvantage that when the contents of the package includes granular or powdered particles, such as ground coffee, particles of the product can get into the deaeration opening and stick there, making it impossible to close the valve tightly. A further disadvantage, if the contents of the package are not rigid, is that shifting of some of the contents deforms the initially flat wall of the packaging container, with the result that strains arise in the unsecured portion of the membrane that covers the opening, so that the valve cannot be opened unless the internal pressure is high. In that case, the package becomes unattractively deformed, and the consumer will suppose that the goods inside have spoiled.
To avoid strain on the valve membrane caused by deformation of the container wall in packaging containers made from flexible packaging material, a pressure relief valve for a packaging container has been developed, for instance such as that disclosed in European Pat. No. A 23703, in which a membrane forming the valve member is secured on an annular support made from relatively rigid material. The support for the membrane is glued firmly to the container wall and prevents deformation of the membrane when the container walls become deformed.